The fantastic platform Redbubble allows anyone to upload designs for free and then shows what they would look like on a t-shirt, coffee mug etc. Members of the public can then buy a t-shirt or coffee mug with your design on it, and you have the option to make some money out of it, but adding a percentage onto the sale price (you determine the percentage).

I have a 0% markup on all my items as I’m not interested in money. But I’ve become completely addicted to making and buying my own designs.